Ohr Chodesh: I will not go through the Mekoros point-by-point from his Sefer, but I will point out one thing. In the Sefer (or possibly his second one), he discusses the concept of a “Treif Begged”. He states that any clothing which began at a certain level of inherent untznius cannot be worn, even if it is made Tznius. For example, a sleeveless dress cannot be worn with a shirt underneath. That is fine. The problem is that such a concept has no source whatsoever in Halachah. No one before this Sefer even mentions such a concept, anywhere (if someone can find me an earlier source in Halachah for this I will retract my statement, but I searched strenuously and did not find anything). And I do not want to discuss further any more similar cases in his Sefarim (which do exist) because I do not want to C”V say anything that I will later regret against someone who without a doubt is a tremendous Talmid Chacham. But it is concepts like this (and others) that allow me to say with confidence that R’ Falk’s Sefarim need not be followed.
(This is not to say that nothing in there is correct. Obviously much of the Sefarim are true Halachah L’ma’aseh. But there are definitely parts that there is much to ask upon.)